What is the immediate treatment protocol for a patient experiencing anaphylaxis?

Anaphylaxis Treatment Protocol

Immediate First-Line Treatment: Epinephrine

Administer intramuscular epinephrine immediately as soon as anaphylaxis is recognized—this is the only first-line treatment and delays in administration are associated with increased mortality. 1, 2

Epinephrine Dosing and Administration

• Adults and adolescents >50 kg: 0.3-0.5 mg of 1:1000 epinephrine IM 2, 3
• Children and prepubertal patients: 0.01 mg/kg IM (maximum 0.3 mg for prepubertal children, 0.5 mg for adults) 2, 3
• Injection site: Mid-outer thigh (vastus lateralis muscle) for optimal absorption 2, 3
• Repeat dosing: Every 5-15 minutes as needed if symptoms persist or recur 1, 2

Critical Actions Concurrent with Epinephrine

• Activate emergency medical services immediately 2
• Position patient supine with lower extremities elevated (unless respiratory distress or vomiting present, then position for comfort) 2, 3
• Never allow patient to stand, walk, or run—this can precipitate cardiovascular collapse 2
• Apply supplemental oxygen for respiratory symptoms 2

Second-Line Adjunctive Treatments (Only AFTER Epinephrine)

These treatments should occur concomitantly but are never substitutes for epinephrine 1:

H1 Antihistamines

• Diphenhydramine: 1-2 mg/kg (maximum 50 mg) IV or oral 1, 3
• Oral liquid formulations are absorbed more rapidly than tablets 1
• Never use antihistamines alone—they have much slower onset than epinephrine 1, 3

H2 Antihistamines (Combined with H1)

• Ranitidine: 1 mg/kg (12.5-50 mg in children, 50 mg in adults) IV over 5 minutes 1
• Combination of H1 and H2 antihistamines is superior to H1 alone but still second-line to epinephrine 1, 3

Bronchodilators

• Albuterol nebulizer: 1.5 mL (child) or 3 mL (adult) every 20 minutes or continuously as needed 1
• MDI: 4-8 puffs (child) or 8 puffs (adult) 1
• Use for bronchospasm resistant to adequate epinephrine doses 1, 3

IV Fluid Resuscitation

• Large volume crystalloid infusion for hypotension, orthostasis, or incomplete response to IM epinephrine 1, 2
• Volume replacement is crucial in severe cases 1

Management of Refractory Anaphylaxis

Persistent Hypotension Despite Epinephrine and Fluids

• Vasopressor infusion (dopamine): 400 mg in 500 mL D5W, infuse at 2-20 mcg/kg/min, titrate to maintain systolic BP >90 mmHg 1, 3
• Requires continuous hemodynamic monitoring 1

Patients on Beta-Blockers

• Glucagon infusion: 1-5 mg IV over 5 minutes (20-30 mcg/kg in children, max 1 mg), followed by 5-15 mcg/min infusion titrated to response 1, 3
• Note: Rapid glucagon administration can induce vomiting 2

Cardiopulmonary Arrest

• High-dose IV epinephrine: 1-3 mg (1:10,000 dilution) slowly over 3 minutes, then 3-5 mg over 3 minutes, then 4-10 mg/min infusion 1
• Children: 0.01 mg/kg (0.1 mL/kg of 1:10,000 solution) every 3-5 minutes; higher doses (0.1-0.2 mg/kg of 1:1,000 solution) for unresponsive arrest 1
• Prolonged resuscitation is encouraged—efforts are more likely successful in anaphylaxis than other causes of arrest 1

Glucocorticoids: Limited Role

• Consider only for: Patients with history of idiopathic anaphylaxis, asthma, or severe/prolonged anaphylaxis 1, 3
• Dosing: 1.0-2.0 mg/kg/day IV every 6 hours, or prednisone 0.5 mg/kg orally for less critical episodes 1, 3
• Important limitation: Glucocorticoids have no role in acute treatment due to slow onset of action; they potentially prevent protracted or biphasic reactions but evidence is weak 1, 3
• Recent evidence suggests glucocorticoids with epinephrine may result in worse outcomes 1

Observation Period

• Minimum 4-6 hours observation in a facility capable of managing anaphylaxis 1, 2
• Prolonged observation or admission warranted for: severe symptoms, refractory symptoms, requirement for multiple epinephrine doses, history of biphasic reactions, or patients with asthma 1, 2
• All patients must be transferred to emergency department, preferably by EMS 2

Discharge Requirements

Before discharge, ensure the following 1, 2, 3:

• Two epinephrine autoinjectors prescribed with proper training on use 2
• Written anaphylaxis emergency action plan 2
• Education on: trigger avoidance, signs/symptoms, biphasic reactions, epinephrine use 1, 2
• Referral to allergist for evaluation 1, 2
• Plan for monitoring autoinjector expiration dates 1

Critical Pitfalls to Avoid

• Delaying epinephrine administration—this is the most common cause of preventable anaphylaxis deaths 1, 2, 4
• Using subcutaneous instead of intramuscular injection—delays absorption 3, 5
• Administering IV epinephrine outside monitored settings—only use for cardiac arrest or profound hypotension unresponsive to IM epinephrine 1, 3
• Relying on antihistamines or glucocorticoids alone—these are never substitutes for epinephrine 1, 3
• Allowing patient to stand or walk—can precipitate cardiovascular collapse 2

High-Risk Populations Requiring Heightened Vigilance

• Adolescents and young adults 1, 2
• Patients with coexisting asthma, especially poorly controlled 1, 2
• Previous history of anaphylaxis 1, 2
• Peanut/tree nut allergies 1
• Patients on beta-blockers 1, 3